QL 

61 

C86 

UBRARY 


UC-NRLF 


B    3    272    33fi 


ZOOLOGY 


BY 


HENRY  EDWARD  CRAMPTON 


PROFESSOR    OF   ZOOLOGY 
COLUMBIA   UNIVERSITY 


)Vew  York 

THE  COLUMBIA  UNIVERSITY  PRESS 
1908 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


ZOOLOGY 


A  LECTURE  DELIVERED  AT  COLUMBIA  UNIVERSITY 

IN  THE  SERIES  ON  SCIENCE,  PHILOSOPHY  AND  ART 

DECEMBER  11,  1907 


ZOOLOGY 


BY 

HENRY  EDWARD  CRAMPTON 


PROFESSOR   OF   ZOOLOGY 
COLUMBIA    mnVEHSITY 


THE  COLUMBIA  UNIVERSITY  PRESS 
1908 


COPYRIGHT,  1908, 
By  THE  COLUMBIA  UNIVERSITY  PRESS. 


Set  up,  and  published  February,  1908. 


•'.< 

ZOOLOGY  ' 


IN  the  present  series  of  addresses  upon  the  nature  and 
scope  of  some  of  the  divisions  of  knowledge,  zoology  con- 
nects the  natural  sciences  with  those  subjects  that  deal  with 
human  progress  in  physical,  social,  political  and  economic 
respects.  Like  the  human  and  other  sciences,  zoology  has 
arisen  from  that  vague  uncoordinated  and  unresolved 
mass  of  knowledge,  the  Natural  Philosophy  of  not  very 
remote  times,  which  undertook  to  comprehend  all  there 
was  of  nature  and  thought.  And  again  like  the  other 
sciences  it  is  as  such  a  branch  of  relatively  late  growth.  In 
earlier  times  few  men  were  sufficiently  withdrawn  from 
the  affairs  of  the  market-place  and  commerce  and  con- 
quest, from  politics  and  government  and  theological  prop- 
aganda, to  observe  the  phenomena  of  nature  closely,  to 
reflect  upon  their  observations,  and  to  summarize  their  de- 
ductions in  the  formularies  of  natural  law.  Not  until 
human  social  structure  neared  the  relatively  settled  condi- 
tion of  modern  times  did  it  become  possible  for  men  to 
differentiate  as  students  of  nature  solely,  rendering  their 
service  to  the  common  weal  as  investigators  of  the  less 
practical  and  more  remote  departments  of  knowledge. 
Now  the  sciences  have  become  so  great,  so  complex  and 
varied,  that  it  is  impossible  for  a  single  mind  to  compre- 
hend all  that  is  included  in  one  of  them.  So  widely  the 
impelling  energy  of  research  has  driven  the  soldiers  of 
investigation  that  only  when,  as  in  the  present  series  of 
addresses,  they  return  to  the  council-fires  of  an  intellectual 

5 


£7673 


bivouac  can  they  come  to  realize  how  far-flung  indeed  are 
the  battle-lines  of  the  armies  of  science — how  rich  and 
diversified  is  the  territory  from  which  knowledge  has 
driven  ignorance  and  superstition.  And  they  must  realize 
also  how  impossible  it  is  for  them  to  conduct  their  opera- 
tions at  all  times  in  entire  independence.  The  results  of 
physics  and  chemistry  are  indispensable  weapons  for  the 
biologist;  geology  takes  the  field  with  paleontology  for 
the  study  of  fossil  forms ;  while  on  the  other  hand  the  ad- 
vance posts  of  zoology  provide  the  students  of  many  a 
human  science  with  a  secure  base  of  operations. 

I  need  not  speak  of  the  inter-relations  of  the  several 
biological  sciences,  for  these  have  been  sufficiently  ex- 
plained in  the  earlier  discourses.  I  shall  pass  directly  to  a 
description  of  the  elements  of  the  present  science  of 
zoology  and  of  its  history,  so  far  as  this  is  necessary  for  a 
clear  understanding  of  the  various  divisions  of  the  subject 
and  of  their  connections;  and  finally  I  shall  endeavor  to 
show  how  through  its  human  materials  zoology  articulates 
directly  with  other  fields  of  knowledge. 


ZOOLOGY  is  the  science  that  deals  with  the  structure,  de- 
velopment and  inter-relationships  of  animals,  with  the 
workings  of  their  parts,  their  activities  and  their  relations 
to  their  environment,  and  with  the  factors  that  determine 
their  forms.  We  may  recognize  two  great  divisions  of  the 
subject,  which  are  concerned  respectively  with  static  and 
with  dynamic  principles,  though  the  materials  of  both 
divisions  are  the  same — namely,  all  animals  throughout  the 
entire  range  from  the  highest  to  the  lowest.  It  is  of  course 
clear  that  morphology — the  science  of  structure — cannot 
be  absolutely  separated  from  physiology — the  science  of 
function  in  its  widest  sense — for  we  do  not  know  of  organic 
structures  that  play  absolutely  no  part  in  an  animal's 

6 


economy,  even  though  this  may  be  a  relatively  passive  one; 
while  on  the  other  hand  we  do  not  know — in  science  at  any 
rate — of  a  function  that  is  devoid  of  a  material  basis.  The 
division  is  made  solely  for  the  sake  of  analysis,  and  it  de- 
pends entirely  upon  the  point  of  view.  Morphology  treats 
adult  animals,  their  different  developmental  stages,  and, 
/  more  naturally,  the  remains  of  extinct  animals  as  though 
they  were  arrested  in  their  living,  but  the  dynamic  aspects 
of  organic  life  are  so  prominent  and  insistent  that  it  is 
really  impossible  to  ignore  them  even  temporarily. 

Besides  dealing  with  the  same  materials,  the  many  com- 
plicated problems  of  zoology  are  still  further  connected  in 
that  the  central  object  of  study  for  both  the  structural  and 
physiological  divisions  is  evolution.  As  we  look  back  over 
the  history  of  the  subject  from  our  modern  vantage- 
ground,  we  can  see  how  zoology  began  with  ancient  and 
mediaeval  natural  history,  how  from  this  parent  stock  arose 
the  additional  separate  branches  of  anatomy,  embryology, 
paleontology  and  distribution,  how  human  physiology  be- 
came comparative  physiology  which  developed  later  into 
the  broad  and  deep  enquiry  into  all  the  activities  of  ani- 
mals, their  vital  relations  to  one  another,  and  their  reac- 
tions to  and  upon  the  environment;  and  we  can  see  how 
all  these  several  branches  were  vitalized  by  the  great  prin- 
ciple of  evolution.  This  whole  history  shows  a  steady 
progress  through  one  phase  after  another  toward  the  mod- 
ern study  of  evolution,  though  the  naturalists  of  the 
eighteenth  and  even  of  much  of  the  nineteenth  century 
were  unconscious,  in  whole  or  in  part,  of  the  way  their  ob- 
servations and  views  were  contributing  to  the  establish- 
ment of  the  doctrine  of  descent  and  to  the  partial  descrip- 
tion that  can  now  be  offered  of  the  natural  factors  of 
evolution.  As  we  shall  see,  the  structural  analysis  of  ani- 
mals demonstrates  the  evolution  of  species  as  a  universal 
process,  while  the  broad  study  of  the  dynamic  relations  of 

7 


animals  is  concerned  with  the  causes  of  this  process,  as 
what  we  may  venture  to  call  the  physiology  of  evolution. 
In  brief,  then,  the  great  questions  of  zoology  are  the  what 
and  the  how  of  evolution. 

In  view  of  the  earlier  lectures,  it  is  unnecessary  to  speak 
at  length  of  classification  or  taxonomy — the  first  division 
of  static  or  structural  zoology.  Aristotle,  who  gathered 
and  studied  some  five  hundred  of  the  more  common  ani- 
mals of  the  earth  and  shore  and  sea,  and  the  mediaevalists 
Wotton  and  Ray,  Gesner  and  Aldrovandi,  were  animated 
primarily  by  the  instincts  of  the  collector  of  interesting 
information.  Linnaeus,  the  great  figure  of  the  eighteenth 
century,  rendered  an  immortal  service  to  zoology  (and 
botany,  too,)  by  introducing  the  present  ordered  system  of 
naming  and  classifying  organisms.  But  classification  was 
to  Linnaeus  an  end  in  itself,  he  could  not  see  that  it  was 
but  a  means  to  the  larger  end  of  understanding  and  ex- 
pressing evolutionary  relationships, — that  resemblance 
meant  consanguinity.  It  remained  for  Erasmus  Darwin, 
the  elder  St.  Hiliare,  Lamarck  and  others  to  appreciate 
this  inner  meaning  which  so  vivifies  the  otherwise  dead 
details  of  taxonomy. 

The  many  connected  details  of  animal  structure  and 
development  and  function  constitute  the  threads,  as  it  were, 
which  are  interwoven  by  comparative  treatment  to  form 
the  warp  and  woof  of  the  fabric  of  zoology.  Classifica- 
tion draws  upon  this  fabric  the  pattern  of  genealogical 
connections,  emphasizing  those  threads  that  run  furthest, 
the  so-called  distinctive  or  diagnostic  characters.  And 
though  the  pattern  must  be  altered  here  and  there  as 
knowledge  increases,  the  zoologist  feels  that  it  has  a  real 
significance  as  a  representation  of  evolutionary  descent. 

As  more  and  more  of  the  lower  animals  were  brought 
by  the  microscope  from  the  obscurity  of  their  zoological 
underworld,  as  exploration  revealed  more  of  the  creatures 

8 


of  previously  unknown  lands,  as  investigation  became 
more  detailed  and  intensive,  comparative  anatomy  arose 
as  an  independent  branch  of  zoology  with  distinct  pur- 
poses of  its  own;  and  it  gained  its  specific  form  and  char- 
acter from  the  studies  of  the  great  zoologists  of  the  early 
nineteenth  century — Lamarck,  Cuvier,  Geoifroy  St.  Hi- 
liare,  Goethe,  Owen,  and  Oken.  These  naturalists  dis- 
sected and  compared  the  various  organic  systems  of  ani- 
mals, following  them  as  widely  as  possible  from  group  to 
group  of  the  numerous  vertebrate  and  invertebrate  forms, 
and  they  and  their  followers  have  placed  the  doctrine  of 
evolution  upon  the  sure  and  broad  foundation  of  com- 
parative anatomy.  The  main  principle  of  this  department 
of  zoology  is  that  the  varied  forms  of  animals  exhibit 
deep-seated  likenesses  that  place  them  in  groups  related 
to  one  another  not  as  the  rungs  of  a  ladder  as  Lamarck 
supposed,  but  rather  as  the  branches  of  a  tree  or  a  bush; 
and  such  branches  again  like  those  of  a  tree  bear  smaller 
branches,  and  these  reach  to  lesser  or  greater  heights  from 
the  base  level  of  primitive  organization.  Thus,  anatomy 
holds  that  community  of  plan  is  an  indication  of  genetic 
affinities,  while  modifications  of  a  common  plan  exhibit  the 
results  of  adaptation  to  different  ends  through  evolution, 
The  framework  of  the  human  arm  is  constructed  out 
of  the  same  elements  with  the  same  arrangement  that 
we  find  in  the  leg  of  a  cat,  the  flipper  of  a  seal,  the  paddle 
of  a  whale,  and  even  the  wing  of  a  bat,  different  though 
these  structures  are  in  function, — and  in  these  resemblances 
comparative  anatomy  discerns  evidence  of  a  remote  com- 
mon ancestry  of  men  and  whales  and  bats. 

Extended  through  the  study  of  tissues,  or  histology,  to 
the  unitary  elements  of  organic  structure — the  cells — com- 
parative analysis  has  brought  the  whole  realm  of  organic 
nature  under  the  sway  of  a  great  principle — the  cell- 
doctrine  of  the  botanist  Schleiden  and  the  zoologist 

9 


Schwann.  This  important  principle,  propounded  in  1838 
and  1839,  produced  an  immediate  effect  in  unifying  or- 
ganic creatures,  though  many  years  passed  before  it  was 
formulated  in  the  terms  employed  to-day.  In  brief,  it  is 
this: — All  the  larger  organisms  are  composed  of  organs 
which  in  turn  are  constructed  of  various  tissues,  like  muscle 
and  nerve  and  connective  elements;  the  tissues  finally  can 
be  resolved  into  units  of  structure,  the  cells,  which  agree 
in  possessing  a  central  body  or  nucleus,  and  in  their  proto- 
plasmic substance.  The  elementary  nature  of  cells  is  still 
further  demonstrated  by  the  simplest  organisms  we  know, 
which  consist  of  one  cell,  nothing  more  and  nothing  less; 
while  finally  the  starting  point  in  the  development  of 
higher  animals  is  always  a  single  cell — the  egg.  Truly 
these  are  remarkable  facts,  when  we  consider  the  wide 
range  of  animal  and  plant  forms. 

Vast  as  the  present  knowledge  is,  the  tasks  of  com- 
parative anatomy  are  not  entirely  completed.  Though 
voyages  of  exploration  like  those  of  the  Beagle  with  Dar- 
win, the  Rattlesnake  with  Huxley,  and  above  all  of  the 
famous  Challenger  have  gone  to  all  parts  of  the  globe, 
though  countless  investigators  have  devoted  their  lives  to 
the  study  of  special  groups  like  birds  and  mammals  and  in- 
sects and  molluscs,  every  year  brings  to  light  new  forms 
that  must  be  analyzed  and  placed ;  while  new  discoveries  in 
other  departments  often  make  it  necessary  to  re-examine 
known  series  in  the  light  of  fuller  knowledge. 

While  many  naturalists  prior  to  the  nineteenth  century 
were  interested  in  the  way  an  animal  egg  produced  an  adult 
organism,  it  was  not  until  the  doctrine  of  descent  energized 
zoology  that  comparative  embryology  attained  the  inde- 
pendent status  that  it  holds  to  this  day.  Harvey  in  1650 
had  perceived  that,  in  his  own  words,  "all  animals  are  in 
some  sort  produced  from  eggs."  Bonnet  and  Haller,  of 
the  early  eighteenth  century,  contended  that  the  germ  was 

10 


a  minute  replica  of  the  adult  which  formed  it,  a  multum  in 
parvo  which  simply  unfolded  and  enlarged  to  produce  an- 
other adult  organism ;  Wolff,  however,  showed  that  this 
view  lacked  a  basis  in  fact,  and  that  as  we  now  universally 
believe,  embryonic  history  is  a  true  development  from  the 
simple  and  unorganized  to  the  progressively  more  and 
more  specialized  later  conditions, — that  it  is,  in  a  word,  an 
epigenesis.  The  great  name  of  the  infancy  of  embryology 
is  that  of  Von  Baer  ( 1792-1876) .  This  acute  observer  and 
thinker  was  struck  by  the  similarity  of  early  stages  in  the 
development  of  quite  different  adult  animals.  Birds  and 
reptiles  and  even  mammals  pass  through  stages  when  they 
possess  gill-slits  like  those  of  fishes,  related  to  heart  and 
blood-vessels  like  the  similar  structures  in  lower  verte- 
brates ;  butterflies  and  flies  and  beetles  are  somewhat  alike 
in  their  larval  stages,  when  as  caterpillars  and  maggots  and 
grubs  they  not  only  resemble  one  another  remarkably  but 
they  are  also  very  like  worms.  Under  the  influence  of  the 
evolution  doctrine,  then  becoming  more  generally  accepted, 
Von  Baer  and  a  host  of  followers  extended  the  science  of 
comparative  embryology  until  Haeckel  in  1866  ventured  to 
state  the  "Law  of  Recapitulation,"  or  the  "Biogenetic 
Law,"  in  the  following  rigid  terms:— Ontogeny  recapitu- 
lates Phylogeny.  (The  development  of  an  individual  re- 
views the  past  history  of  its  species. )  Led  by  their  enthu- 
siasm many  of  the  later  nineteenth  century  zoologists  fol- 
lowed too  implicitly  the  lines  of  the  embryonic  record, 
though  Haeckel  himself,  the  most  radical  advocate  of  the 
law,  pointed  out  that  there  are  many  serious  omissions  in 
the  narrative,  that  false  passages  are  inserted  as  the  result 
of  purely  larval  and  embryonic  needs  and  adaptations, 
while  many  alterations  in  the  way  of  anachronisms  have 
been  made.  Of  late  years  there  has  been  a  strong  reaction 
from  the  complete  acceptance  of  the  principle  as  a  reliable 
mode  of  interpreting  embryonic  histories.  But  I  believe 

11 


zoologists  generally  feel  that  used  with  due  caution  the  law 
has  a  high  value  for  the  student  of  evolution,  and  they  real- 
ize that  embryology  is  perhaps  more  significant  in  other  re- 
spects than  in  showing  exactly  how  in  past  times  any  given 
species  has  evolved.  The  present  tasks  in  this  department, 
now  so  thoroughly  investigated,  are  to  distinguish  between 
the  false  and  the  true  portions  of  the  record,  between  the 
new  and  the  old,  and  to  ascertain  the  physiology  of  devel- 
opment, in  order  to  gain  a  more  complete  knowledge  of 
racial  history  and  of  the  dynamics  of  organic  nature. 

The  study  of  the  fossil  remains  of  animal  organisms,  or 
paleontology,  is  the  fourth  division  of  structural  zoology, 
which  as  an  independent  branch  dates  back  to  the  time  of 
Cuvier,  scarcely  a  hundred  years  ago.  Vestiges  of  creation 
were  indeed  known  long  before  that  time,  but  they  were 
variously  regarded  as  freaks  of  geological  formation,  lusus 
naturce,  as  remains  of  creatures  stranded  by  tidal  waves  or 
cataclysms  like  the  traditional  flood,  or  again  as  the  re- 
mains of  animals  formed  by  a  process  of  spontaneous  gen- 
eration in  the  depths  of  the  earth  that  had  failed  to  reach 
the  surface.  It  was  Leonardo  da  Vinci  of  the  fifteenth 
century  who,  anticipating  the  naturalists  of  later  times,  be- 
lieved these  vestiges  are  what  common-sense  says  they  are 
—simply  relics  of  creatures  that  lived  when  the  earth  was 
younger.  Cuvier  was  in  a  true  sense  the  founder  of  pale- 
ontology; though  a  special  creationist,  he  recognized  that 
beneath  their  differences  there  were  fundamental  likenesses 
between  recent  and  extinct  animals.  He  assumed  that  cata- 
clysms had  closed  the  several  geologic  epochs  whereupon 
new  series  of  animals  and  plants  were  created  upon  the 
same  general  working-plans  employed  in  earlier  ages ;  thus 
he  combined  the  idea  of  change  in  geologic  time  with  a  be- 
lief in  supernatural  creation.  When,  however,  Lyell  led 
geologists  and  others  to  abandon  the  cataclysmic  hypo- 
thesis in  favor  of  the  doctrine  of  uniformitarianism,  when 

12 


the  series  of  known  fossil  forms  increased  and  the  intrinsic 
value  of  the  paleontological  evidence  became  clearer,  the 
doctrine  of  evolution  finally  claimed  this  field  also  as  its 
own. 

The  nature  of  the  case  is  such  that  the  fossil  record  must 
remain  incomplete,  perhaps  forever.  For  not  all  the  ani- 
mals of  former  times  possessed  hard  parts  capable  of  re- 
sisting the  disintegrating  forces  of  organic  and  inorganic 
nature,  the  rocky  tombs  of  those  animals  that  were  em- 
bedded in  the  sands  and  silts  have  been  crushed  and  rent 
asunder  by  the  very  geological  agencies  that  at  first  con- 
structed them.  More  than  half  of  the  earth's  surface  is  now 
under  water,  while  by  no  means  all  of  the  dry  land  is  ac- 
cessible. Only  a  few  scratches  have  been  made  here  and 
there  upon  the  earth's  hard  crust,  so  it  is  little  wonder  that 
the  testimony  of  the  rocks  is  halting  and  imperfect.  But 
what  there  is,  a  rapidly  growing  body  of  cold,  hard  facts, 
is  in  itself  conclusive  evidence  of  the  reality  of  evolution. 
Researches  like  those  of  Von  Zittel,  Cope,  Hyatt,  Marsh, 
Osborn,  and  Scott,  demonstrate  that,  when  they  appear  at 
all,  the  great  groups  or  phyla  of  animals  and  their  sub- 
divisions succeed  one  another  in  that  chronological  order 
which  comparative  anatomy  and  embryology  have  inde- 
pendently shown  is  the  order  of  their  evolution.  Then  too 
there  are  those  fossil  types  that  link  together  groups  now 
so  widely  separated,  like  Archaeopteryx,  which  is  at  once 
a  feathered  reptile  and  a  bird  with  reptilian  tail  and  skull 
and  limbs.  And  there  are  the  marvelously  perfect  series 
of  fossils  like  those  which  demonstrate  the  evolution  of 
modern  horses  and  elephants;  and  finally,  as  the  special 
creationist  Louis  Agassiz  himself  showed,  some  fossil 
series  parallel  very  closely  the  embryonic  record  in  modern 
types.  No  field  opens  more  invitingly  than  that  of  the 
paleontologist.  His  tasks  are  to  search  the  rocks  every- 
where for  new  fossil  types  to  fill  in  the  gaps  of  the  lines  of 

13 


descent  that  at  best  can  only  be  interrupted  lines,  and  to 
show  how  these  lines  lead  to  modern  forms  or  to  divergent 
kinds  that  have  ceased  to  be.  And  he  will  compare  his  re- 
sults with  those  of  students  in  other  fields,  who  will  assist 
him  to  formulate  the  working-plans  for  his  own  labors. 

Zoo-geography  is  the  last  branch  of  structural  zoology 
to  attain  an  independent  status.  Many  observers  from 
Buff  on  onward  had  been  struck  by  the  fact  that  species  of 
animals  are  not  uniformly  distributed  over  the  earth,  that 
they  differ  more  widely  as  the  observer  passes  to  more  and 
more  remote  localities,  with  more  different  climatic  and 
other  environmental  conditions.  But  the  meaning  of  these 
peculiarities  was  obscure  until  the  doctrine  of  descent 
cleared  their  vision.  Wagner,  Louis  Agassiz,  and  Dana, 
Sclater,  Murray,  and  Wallace  were  the  leaders  of  those  who 
have  brought  together  the  immense  mass  of  modern  knowl- 
edge of  animal  distribution.  From  this  many  well-estab- 
lished principles  relating  to  descent  have  been  derived, 
though  these  have  a  deeper  interest  in  connection  with  the 
dynamic  problem  as  to  whether  differences  in  environment 
can  actually  cause  species  to  transform,  as  Lamarck  sup- 
posed. As  a  statement  of  the  results  in  this  apparently 
simple,  but  really  quite  complicated  field  would  be  mislead- 
ing, I  fear,  from  its  brevity  and  general  form,  I  will  ven- 
ture to  present  just  one  conclusion.  Geographical  isola- 
tion corresponds  in  a  general  way  with  the  divergence  of 
species  in  their  evolution  from  common  ancestors;  thus 
widely  separated  areas  have  faunas  that  differ  more  widely 
in  zoological  respects  than  do  those  of  neighboring  or  con- 
nected countries.  For  example,  the  Australian  region  has 
been  cut  off  for  a  relatively  long  period  from  neighboring 
continents,  and  in  correspondence  with  this  isolation  it  con- 
tains the  only  egg-laying  mammals  known,  as  well  as  all  of 
the  pouched  mammals  like  the  kangaroo,  with  a  few  ex- 
ceptions like  our  American  opossum.  Furthermore,  groups 

14 


of  isolated  oceanic  islands,  like  the  Galapagos  and  Azores 
and  the  clusters  of  Polynesia,  are  inhabited  by  lizards  and 
birds  and  insects  which  resemble  most  closely  the  species 
of  the  nearest  bodies  of  land.  Such  resemblances  are  most 
reasonably  interpreted  as  indicating  that  the  original  pro- 
genitors of  the  island  colonies  were  stragglers  from  the 
nearest  mainland,  whose  descendants  have  undergone  di- 
vergent evolution  during  succeeding  generations. 

Having,  then,  this  vast  store  of  fact  and  principle 
amassed  through  centuries  by  countless  students,  the  zool- 
ogist is  entitled  to  speak  positively  when  he  finds  a  law  like 
the  doctrine  of  evolution  that  reviews  and  summarizes  the 
whole  range  of  animal  structure.  The  well-established 
facts  of  zoology  are  the  reasons  why  he  asserts  with  a  de- 
cision often  mistaken  for  dogmatism  that  evolution  is  a 
real  process.  The  further  question,  why  is  nature  so  con- 
stituted that  evolution  is  true,  is  an  enquiry  that  does  not 
fall  within  the  limits  of  zoological  science. 

We  now  come  to  the  second  great  division  of  zoology, 
which  as  a  whole  is  concerned  with  broad  and  deep  enquiry 
into  the  workings  of  nature ;  it  is  natural  history  in  the  best 
sense.  Prior  to  the  time  of  Darwin  attempts  to  solve  the 
kinetic  problems  of  the  organic  world  were  hampered  by 
anthropomorphism  and  narrowness  of  view,  as  well  as  by 
paucity  of  facts.  But  since  then,  owing  to  the  immense 
influence  of  the  works  of  that  great  naturalist,  so  much  at- 
tention has  been  given  to  the  fundamental  problems  of 
life  that  it  is  now  possible  to  correlate  many  principles 
which  describe  not  only  the  fact  of  evolution  but  many  of 
the  factors  as  well.  And  in  this  modern  development  wide 
observation  has  led  so  directly  to  extensive  experiment  that 
we  may  justly  characterize  the  present  period  as  an  age  of 
experimental  zoology.  Just  as  all  the  apparently  discon- 
nected studies  of  structural  zoology  deal  with  one  mat- 
ter,— evolution, — so  in  the  sphere  of  experimental  zoology 

15 


all  the  radii  converge  upon  the  study  of  the  factors  and 
method  of  species  transformation. 

We  can  only  mention  some  of  the  modern  departments 
which  have  yielded  brilliant  results,  such  as  cytology,  ex- 
perimental embryology,  experimental  fertilization,  and 
regeneration.  But  we  may  point  out  that  the  general 
problems  in  these  various  fields  deal  like  the  problem  of 
evolution  itself  with  an  analysis  of  the  internal  and  ex- 
ternal influences  that  determine  the  final  adult  conditions 
of  species.  For  example,  the  adult  salamander  possesses  a 
specific  structure,  in  a  state  of  balance  or  adaptation,  that 
is  the  final  result  of  an  evolution  process  up  to  the  present 
time ;  this  same  specific  condition  is  the  goal  of  the  changes 
through  which  the  salamander's  egg  and  embryo  pass  in 
development;  it  is  the  goal  also  that  may  be  reached  by 
even  a  portion  of  a  divided  salamander's  egg;  while  finally 
it  is  the  goal  of  the  regenerative  processes  that  enable  a 
salamander  from  which  a  leg  has  been  cut  off  to  reproduce 
the  missing  part.  Everything  centers  then  about  the  ques- 
tion as  to  the  origin  of  adult  specific  forms,  which  exhibit 
adaptation. 

Realizing  this,  we  may  pass  on  immediately  to  consider 
how  through  the  study  of  adaptation,  Darwin  was  led  to 
formulate  his  potent  theories,  which  have  been  the  basis  for 
recent  progress.  As  the  other  speakers  upon  biological 
sciences  have  already  stated,  the  most  striking  feature  of 
animals  and  plants  is  their  adjustment  to  their  vital  condi- 
tions. An  organism  that  seems  so  sufficient  unto  itself,  so 
capable  and  independent,  is  nevertheless  inextricably  in- 
terlocked with  its  surroundings,  for  its  very  substance  is 
composed  of  materials  which  with  their  endowments  of 
energy  have  been  wrested  from  the  environment.  An 
animal  that  is  pressed  upon  by  the  substances  of  the  outer 
world,  that  is  played  upon  by  various  energies,  and  is 
attacked  on  all  sides  by  innumerable  foes,  finds  itself  in- 

16 


volved  in  a  warfare  that  is  tragically  one-sided;  and  it 
must  prevail  over  all  its  many  foes  or  it  must  acknowledge 
defeat  and  pay  the  penalty  for  unconditional  surrender, 
which  is  death, — so  stern  and  unyielding  is  that  vast  total- 
ity we  individualize  as  the  environment.  The  generalized 
biological  formula,  then,  for  the  turmoil  of  nature  is 
adaptation=life. 

Here  then  is  the  heart  of  the  mystery.  How  has  this 
universal  condition  of  adaptation  been  brought  about? 
What  have  animals  within  them  that  might  determine  their 
greater  or  less  efficiency?  What  external  influences,  if 
any,  are  capable  of  directing  the  efforts  of  living  creatures 
to  meet  their  enemies?  How  are  modifications  perpetuated 
when  they  have  arisen?  To  many  of  these  questions  Dar- 
win, Weismann,  Mendel,  De  Vries,  and  others  have  found 
answers,  not  complete  or  perfect,  it  is  true,  but  they  have 
relegated  to  the  past  the  former  reply  that  supernatural 
causes  must  be  invoked  to  account  for  nature.  Science  is 
convinced  that  the  study  of  nature's  workings  at  the 
present  time  reveals  natural  factors  which  are  competent 
to  account  for  much  of  the  wonderful  process  of  evolu- 
tion. 

As  everyone  knows,  the  works  of  Darwin  inaugurated 
our  recent  era  in  biology.  In  1858,  Darwin  and  Wallace 
announced  the  doctrine  of  natural  selection,  and  in  1859, 
Darwin  published  the  "Origin  of  Species,"  a  book  that  has 
proved  a  veritable  Magna  Charta  of  intellectual  liberties, 
for  as  no  other  single  document  before  or  since  it  has  released 
the  thoughts  of  men  from  the  trammels  of  unreasoned  con- 
servatism and  dogmatism.  And  its  influence  has  been  felt 
far  beyond  the  borders  of  biological  science — it  has  ex- 
tended to  the  very  confines  of  organized  knowledge  every- 
where. But  it  is  a  mistaken  popular  notion,  and  one  of  the 
hardest  to  drive  from  the  mind  of  the  layman  in  science, 
that  Darwin  founded  the  doctrine  of  evolution  by  the  book 

17 


mentioned  and  those  that  followed.  The  fact  of  evolu- 
tionary descent  had  been  established  long  before,  while 
even  some  of  the  special  points  of  Darwin's  theories  as  to 
method  had  been  anticipated.  Had  Darwin  never  lived, 
I  believe  that  evolution  would  still  be  accepted  and 
taught  at  the  present  day.  But  Darwin  rendered  two 
immortal  services  to  science.  During  the  twenty  years 
that  elapsed  between  the  first  conception  of  his  theories 
and  the  date  of  their  publication,  he  marshalled  in  orderly 
array  all  the  biological  data  obtainable  which  proved  the 
transformation  of  species,  including  the  previously  un- 
recognized body  of  evidence  afforded  by  the  domesticated 
animals.  In  the  second  place,  in  his  doctrine  of  natural 
selection  he  presented  for  the  first  time  a  partial  consistent 
program  of  nature's  method  of  accomplishing  evolution. 
Darwin  did  not  believe  that  this  explanation  was  final  or 
even  complete,  whatever  his  opponents  of  the  time  or 
critics  of  the  present  might  contend. 

What  now,  is  the  doctrine  of  natural  selection,  as  Darwin 
propounded  it?  All  animals  vary;  every  individual  differs 
from  others  of  its  kind,  even  from  its  closest  kin  and  from 
its  parents  in  some  or  many  particulars  and  to  different 
degrees.  Whatever  the  causes,  the  fact  of  variation  stands 
unquestioned.  Some  variations  are  of  course  due  to  direct 
environmental  influence,  and  to  these  Buff  on  attributed  an 
excessive  importance;  other  deviations  from  the  parental 
or  average  specific  type  are  no  doubt  due  to  indirect  effects 
of  the  environment,  as  Lamarck  contended.  But  there  are 
countless  other  variations  that  cannot  be  so  explained, 
some  of  them  indeed  appearing  before  an  individual  is  sub- 
jected to  the  action  of  the  environment,  and  these  are  the 
congenital  variations  due  to  some  constitutional  even  if 
unknown  causes.  These  seemed  to  Darwin  to  be  the  most 
important  in  evolution. 

The  second  element  of  the  doctrine  is  that  over-produc- 

18 


tion,  or  rather  over-reproduction,  is  a  universal  character- 
istic of  living  things.  The  normal  rate  of  multiplication 
is  such  that  any  given  form  of  animal  or  plant  would 
cumber  the  earth  or  fill  the  sea  in  a  relatively  brief  period 
of  time.  We  now  know  that  a  bacillus  less  than  %ooo  of 
an  inch  in  length  multiplies  under  normal  conditions  at  a 
rate  that  would  cause  the  offspring  of  a  single  individual 
to  fill  the  ocean  to  the  depth  of  a  mile  in  five  days.  "Slow- 
breeding  man,"  wrote  Darwin,  "has  doubled  in  the  past 
twenty-five  years."  But  excessive  multiplication  is  checked 
by  the  third  part  of  the  whole  process,  namely,  the  struggle 
for  existence,  that  fierce  unequal  warfare  waged  by  every 
individual  with  its  inorganic  surroundings,  with  other 
species  of  living  things,  and  with  others  of  its  own  kind. 
Indeed  where  members  of  the  same  species  compete,  the 
struggle  often  surpasses  in  ferocity  the  warfare  with  other 
organisms.  Communal  organisms  only  are  in  part  excep- 
tions, for  in  these  the  battle  involves  the  clash  of  com- 
munity with  community  more  than  it  does  the  interests  of 
the  individuals  of  a  single  colony.  To  what,  now,  do  these 
elemental  processes  lead,  asks  Darwin.  Though  all  seek 
to  maintain  themselves,  all  cannot  possibly  live  when  only 
a  few  can  find  sustenance  or  can  escape  their  enemies. 
Naturally  those  which  possess  any  advantage  whatsoever, 
that  vary  ever  so  slightly  in  the  direction  of  better  adjust- 
ment would  survive  where  their  brethren  perish.  And  this 
is  nature's  selective  process,  with  its  positive  and  negative 
aspects — the  survival  of  the  fittest  and  the  elimination  of 
the  unfit.  Now  we  can  see  why  adaptation  is  a  universal 
characteristic  of  species — there  are  no  unadapted.  If 
such  there  were,  they  have  fallen  long  ago,  and  the  world 
knows  them  no  more.  True  it  is  that  perfection  is  not 
attained  by  any  creature,  but  it  must  establish  a  modus 
Vivendi  or  it  perishes.  Thus,  Darwin  held,  nature  perfects 
species  by  dealing  directly  with  favoring  derivations  that 

19 


are  mainly  congenital,  and  so  through  these  it  selects  the 
hereditary  factors  that  determine  favorable  variations. 

In  one  fundamental  respect  the  doctrine  is  incomplete, 
as  it  fails  to  explain  the  causes  for  the  variations  with 
which  selection  deals.  It  accounts  for  the  perpetuation  of 
favoring  variations,  but  it  does  not  account  for  their  incep- 
tion. Because  of  this  defect,  investigators  reacted  from 
the  academic  discussion  of  Darwin's  original  doctrine,  and 
returned  to  deeper  and  wider  study  of  heredity  and  varia- 
tion with  brilliant  success.  Some  neo-Darwinians  have  en- 
deavored to  make  the  selective  process  an  originative 
influence— notably  Roux,  and  Weismann  in  his  theory  of 
germinal  selection.  Darwin  himself  added  the  subsidiary 
process  of  sexual  selection,  which  regards  the  preference 
by  one  sex  of  characteristics  of  the  opposite  sex  as  a  con- 
serving influence.  But  while  such  attempts  have  failed, 
zoologists  believe,  to  explain  the  whole  method  of  evolu- 
tion, much  of  the  process  has  been  demonstrated  more  and 
more  clearly  with  further  study.  The  laws  of  fluctuating 
variations  have  now  been  formulated  with  mathematical 
accuracy,  through  the  employment  of  the  statistical 
methods  used  earlier  by  anthropologists  like  Quetelet.  The 
studies  of  Galton,  and  Pearson,  Boas,  Weldon,  and  Da- 
venport have  demonstrated  that  structural  and  physio- 
logical characters  of  men,  of  other  animals,  and  of  plants 
as  well,  vary  according  to  the  formulas  of  chance  or  error, 
— a  result  they  say  that  follows  from  the  combined  influ- 
ence of  innumerable  and  independent  factors.  Variation 
is  a  natural  phenomenon  of  chance.  Furthermore,  the 
reality  of  the  selective  process  has  also  been  proved  by 
statistical  methods.  Bumpus'  English  sparrows,  Weldon's 
snails  and  crabs,  and  many  other  cases  show  that  the  indi- 
viduals which  depart  widely  from  an  average  condition,  or 
that  are  uncorrelated  in  their  organization,  are  marked  for 
destruction. 

20 


In  brief,  while  natural  selection  has  not  been  established 
as  in  any  sense  an  originative  process,  it  has  been  demon- 
strated, I  believe,  as  a  judicial  process.  For  we  may  liken 
the  many  varied  vital  conditions  to  jurymen,  before  whom 
every  organism  must  present  itself  for  judgment;  and  a 
unanimous  verdict  of  complete  or  at  least  partial  approval 
must  be  rendered,  or  the  organism  must  perish. 

The  phenomena  of  biological  inheritance,  however,  have 
demanded  the  greater  attention  of  Darwinian  and  post- 
Darwinian  investigators.  A  complete  statement  of  the 
whole  of  evolution  must  show  how  species  maintain  the 
same  general  characteristics  through  inheritance,  how  the 
type  is  held  true  with  passing  generations,  and  it  must  also 
show  how  new  characters  may  enter  into  the  heritage  of 
any  species  to  be  transmitted  as  organisms  transform  in 
evolution. 

The  earliest  naturalists  had  accepted  the  fact  of  inheri- 
tance as  self-sufficient.  The  resemblance  between  parent 
and  offspring  did  not  demand  an  explanation  any  more 
than  variation.  When  Buff  on,  however,  added  the  ele- 
ment of  species  transformation,  he  held  that  external 
influences  could  bring  about  a  directly  responsive  organic 
change,  which  he  assumed  was  inherited.  Lamarck  devel- 
oped the  well-known  view,  previously  advocated  by  Eras- 
mus Darwin,  that  indirect  responses  to  the  environment 
could  be  fixed  in  inheritance  as  so-called  "acquired  charac- 
ters," meaning  by  this  phrase  that  such  characters  are 
acquisitions  during  the  life-time  of  an  individual  as  the 
effects  of  disuse  or  unusual  use,  or  of  new  habits.  Coming 
again  to  Darwin,  we  find  that  he  endeavored  to  support 
Lamarck's  doctrine  and  to  supplement  his  doctrine  of 
selection  by  adding  the  theory  of  pangenesis.  According 
to  this  every  cell  of  every  tissue  and  organ  of  the  body 
produces  minute  particles  called  gemmules,  which  partake 
of  the  characters  of  the  cells  that  produce  them.  The 

21 


gemmules  were  supposed  to  be  transported  throughout 
the  entire  body,  and  to  congregate  in  the  germ-cells,  which 
would  be  in  a  sense  minute  editions  of  the  body  which 
bears  them,  and  would  so  be  capable  of  producing  the  same 
kind  of  a  body.  If  true,  this  view  would  lead  to  the  accept- 
ance of  Lamarck's  or  even  Buffon's  doctrine,  for  changes 
induced  in  any  organ  by  other  than  congenital  factors 
could  be  impressed  upon  the  germ-cell,  and  would  then  be 
transported  together  with  the  original  specific  characters 
to  future  generations.  Darwin  was  indeed  a  good  La- 
marckian. 

But  the  researches  of  post-Darwinians,  and  especially 
those  of  the  students  of  cellular  phenomena,  have  demon- 
strated that  such  a  view  has  no  real  basis  in  fact.  Many 
naturalists  like  Naegeli  and  Wiesner  were  convinced  that 
there  was  a  specific  substance  concerned  with  hereditary 
qualities  as  in  a  larger  wray  protoplasm  is  the  physical  basis 
of  life.  It  remained  for  Weismann  to  identify  this  theo- 
retical substance  with  a  specific  part  of  the  cell,  namely, 
the  deeply-staining  substance,  or  chromatin,  contained  in 
the  nucleus  of  every  cell.  Bringing  together  the  accumu- 
lating observations  of  the  numerous  cytologysts  of  his 
time,  and  utilizing  them  for  the  development  of  his  some- 
what speculative  theories,  Weismann  published  in  1882  a 
volume  called  "The  Germ-Plasm,"  which  is  an  immortal 
foundation  for  the  later  work  on  inheritance.  The  essen- 
tial principles  of  the  germ-plasm  theory  are  somewhat  as 
follows :  The  chromatin  of  the  nucleus  contains  the  de- 
terminants of  hereditary  qualities.  In  reproduction,  the 
male  sex -cell,  which  is  scarcely  more  than  a  minute  mass  of 
chromatin  provided  with  a  thin  coat  of  protoplasm  and 
a  motile  organ,  fuses  with  the  egg,  and  the  nuclei  of  the 
two  cells  unite  to  form  a  double  body,  which  contains  equal 
contributions  of  chromatin  from  the  two  parental  organ- 
isms. This  gives  the  physical  basis  for  paternal  inheri- 

22 


tance  as  well  as  for  maternal  inheritance,  and  it  shows  why 
they  may  be  of  the  same  or  equivalent  degree.  When, 
now,  the  egg  divides,  at  the  first  and  later  cleavages,  the 
chromatin  masses  or  chromosomes  contained  in  the  double 
nucleus  are  split  lengthwise  and  the  twin  portions  separate 
to  go  into  the  nuclei  of  the  daughter  cells.  As  the  same 
process  seems  to  hold  for  all  the  later  divisions  of  the 
cleavage-cells  whose  products  are  destined  to  be  the  vari- 
ous tissue  elements  of  the  adult  body,  it  follows  that  all 
tissue-cells  would  contain  chromatin  determinants  derived 
equally  from  the  male  and  female  parents.  As  of  course 
only  the  germ-cells  of  an  adult  organism  pass  on  to  form 
later  generations,  and  as  their  content  of  chromatin  is 
derived  not  from  the  sister-organs  of  the  body  but  from 
the  original  fertilized  egg,  there  is  a  direct  stream  of  the 
germ-plasm  which  flows  continuously  from  germ-cell  to 
germ-cell  through  succeeding  generations.  This  stream, 
be  it  noted,  does  not  flow  circuitously  from  egg  to  adult 
and  then  to  new  germ-cells,  but  it  is  direct  and  continuous, 
and  apparently  it  cannot  pick  up  any  of  the  body-changes 
of  an  acquired  nature ;  indeed,  it  is  doubtful  whether  such 
changes  can  reach  the  germ-cells  at  all,  for  the  path  is  not 
traversed  in  that  retrograde  direction. 

It  must  be  clear,  I  am  sure,  that  this  theory  supplements 
natural  selection,  as  it  describes  the  physical  basis  of  inher- 
itance, it  demonstrates  the  efficiency  of  congenital  or 
germ-plasmal  factors  of  variation  in  contrast  with  the 
Lamarckian  factors,  and  finally  in  the  way  that  in  the 
view  of  Weismann  it  accounts  for  the  origin  of  variations 
as  the  result  of  the  commingling  of  two  differing  parental 
streams  of  germ-plasm. 

At  first,  for  many  reasons  Weismann's  theories  did  not 
meet  with  general  acceptance,  but  during  recent  years 
there  has  been  a  marked  return  to  many  of  his  posi- 
tions, mainly  as  the  result  of  further  cytological  discov- 

23 


cries,  and  of  the  formulation  of  Mendel's  Law  and  of 
De  Vries'  Mutation  Theory.  The  first-named  law  was  pro- 
pounded by  Gregor  Mendel  on  the  basis  of  extensive  ex- 
periments upon  plants  conducted  during  many  years, 
from  1860  on,  in  the  obscurity  of  his  monastery  garden  at 
Altbriinn,  in  Germany.  It  was  rescued  from  oblivion 
by  De  Vries  who  found  it  buried  in  a  mass  of  literature  and 
brought  it  to  light  when  he  published  his  renowned  Muta- 
tion Theory  in  1901.  Mendelian  phenomena  of  inheri- 
tance, confirmed  and  extended  by  numerous  workers  with 
plants  and  animals,  prove  that  in  many  cases  portions  of 
streams  of  germ-plasm  that  combine  to  form  the  hered- 
itary content  of  organisms  may  retain  their  individuality 
during  embryonic  and  later  development,  and  that  they 
may  emerge  in  their  original  purity  when  the  germ-cells 
destined  to  form  a  later  generation  undergo  the  prepara- 
tory processes  called  maturation.  They  demonstrate  also 
the  apparent  chance  nature  of  the  phenomena  of  inheri- 
tance. I  think  the  most  striking  and  significant  result  in 
this  field  is  the  proof  that  a  particular  chromosome  or  chro- 
matin  mass  determines  a  particular  character  of  an  adult 
organism,  which  is  quite  a  different  matter  from  the 
reference  of  all  the  hereditary  characters  to  all  of  the 
chromatin.  Professor  Wilson  has  brought  forward  the 
convincing  data  showing  that  the  complex  character  of  sex 
in  insects  actually  resides  in  or  is  determined  by  particular 
and  definite  masses  of  this  wonderful  basis  of  inheritance. 
Mendel's  principles  also  account  in  the  most  remarka- 
ble way  for  many  previously  obscure  phenomena,  such  as 
reversion,  and  again,  the  case  where  a  child  resembles  its 
grandparent  more  than  either  of  its  parents;  these  seem 
to  be  due,  so  to  speak,  to  the  rise  to  the  surface  of  a  hidden 
stream  of  germ-plasm  that  had  flowed  for  one  or  many 
generations  beneath  its  accompanying  currents.  I  believe 
that  the  law  is  replacing  more  and  more  the  laws  of  Gal- 

24 


ton  and  Pearson,  formulated  as  statistical  summaries  of 
certain  phenomena  of  human  inheritance  taken  en  masse. 
According  to  Galton's  celebrated  law  of  ancestral  inheri- 
tance, the  qualities  of  any  organism  are  determined  to  the 
extent  of  a  certain  fraction  by  its  two  parents  taken  to- 
gether as  a  mid-parent,  that  a  smaller  definite  fraction  is 
contributed  by  the  grandparents  taken  together  as  a  mid- 
grandparent,  and  so  on  to  earlier  generations.  But  Men- 
del's Law  has  far  greater  definiteness,  it  explains  more 
accurately  the  cases  of  alternative  inheritance,  and  it  may 
be  shown  to  hold  for  blended  and  mosaic  inheritance  as  well. 

De  Vries'  Mutation  Theory  has  already  been  explained 
in  an  earlier  address  by  Professor  Richards.  It  is  clearly 
not  an  alternative  but  a  complementary  theory  to  Natural 
Selection,  the  Germ-Plasm  and  Mendelian  Theories.  Like 
these  last,  it  emphasizes  the  importance  of  the  congenital 
hereditary  qualities  contained  in  the  germ-plasm,  though 
unlike  the  Darwinian  doctrine  it  shows  that  sometimes  new 
forms  may  arise  by  sudden  leaps  and  not  necessarily  by  the 
slow  and  gradual  accumulation  of  slight  modifications  or 
fluctuations.  The  mutants  like  any  other  variants  must  pre- 
sent themselves  before  the  jury  of  environmental  circum- 
stances, which  passes  judgment  upon  their  condition  of 
adaptation,  and  they  too  must  abide  by  the  verdict  that 
means  life  or  death. 

From  what  has  been  said  of  these  post-Darwinian  dis- 
coveries, the  Lamarckian  doctrine,  which  teaches  that  ac- 
quired non-congenital  characters  are  transmitted,  seems 
to  be  ruled  out.  I  would  not  lead  you  to  believe  that  the 
matter  is  settled.  I  would  say  only  that  the  non-transmis- 
sion of  racial  mutilations,  negative  breeding  experiments 
upon  mutilated  rats  and  mice,  the  results  of  further  study 
of  supposedly  transmitted  immunity  to  poisons — that  all 
these  have  led  zoologists  to  render  the  verdict  of  "not 
proved."  The  future  may  bring  to  light  positive  evidence, 

25 


and  cases  like  Brown-Sequard's  guinea  pigs,  and  results 
like  those  of  MacDougal  with  plants  and  of  Tower  with 
beetles  may  lead  us  to  alter  the  opinion  stated.  But  as  it 
stands  now  most  investigators  hold  that  there  are  strong 
general  grounds  for  disbelief  in  the  principle,  and  also 
that  it  lacks  experimental  proof. 

The  explanation  of  natural  evolution  given  by  Darwin- 
ism and  the  principles  of  Weismann,  Mendel  and  De 
Vries,  still  fails  to  solve  the  mystery  completely,  and  ap- 
peal has  been  made  to  other  agencies,  even  to  teleology 
and  to  "unknown"  and  "unknowable"  causes  as  well  as 
to  circumstantial  factors.  A  combination  of  Lamarckian 
and  Darwinian  factors  has  been  proposed  by  Lloyd  Mor- 
gan, Mark  Baldwin,  and  Professor  Osborn,  in  the  Theory 
of  Organic  Selection.  The  Theory  of  Orthogenesis  pro- 
pounded by  Naegeli  and  Eimer,  now  gaining  much 
ground,  holds  that  evolution  takes  place  in  direct  lines  of 
progressive  modification,  and  is  not  the  result  of  apparent 
chance.  Of  these  and  similar  theories,  all  we  can  say  is 
that  if  they  are  true,  they  are  not  so  well-substantiated  as 
the  ones  we  have  reviewed  at  greater  length. 

The  task  of  experimental  zoology  is  to  work  more 
extensively  and  deeply  upon  inheritance  and  variation, 
combining  the  methods  and  results  of  cellular  biology, 
biometrics,  and  experimental  breeding.  We  may  safely 
predict  that  great  advances  will  be  made  during  the  next 
few  years  in  analyzing  the  method  of  evolution ;  and  that 
a  few  decades  hence  men  will  look  back  to  the  present  time 
as  a  period  of  transition  like  the  era  of  re-awakened  inter- 
est and  renewed  investigation  that  followed  the  appear- 
ance of  the  "Origin  of  Species." 


WE  must  now  state   distinctly  and   fairly  the   present 
views  of  science  regarding  man's  place  in  nature.    Surely 

26 


human  evolution  is  a  subject  that  falls  within  the  scope  of 
zoological  investigation,  unless  indeed  it  can  be  shown  that 
the  human  species  is  exempt  from  the  control  of  those 
laws  of  nature  that  hold  sway  over  the  animate  world 
elsewhere,  unless  something  can  be  found  which  excludes 
man  from  the  animal  kingdom.  Notwithstanding  the  most 
prolonged  search  not  only  by  zoologists  but  as  well  by  those 
who  have  been  unfriendly  to  the  doctrine  of  descent,  the 
study  of  man  and  of  men  has  revealed  nothing  essentially 
unique.  What  is  known  of  the  anatomy,  development  and 
fossil  relations  of  man  is  summarized  in  the  statement  that 
he  belongs  to  the  genus  and  species  Homo  sapiens,  placed 
with  the  apes  and  some  other  forms  in  the  order  primates 
because  of  agreement  in  certain  peculiar  details.  The 
primates  agree  with  the  carnivora,  rodents  and  many  other 
orders  in  the  characteristics  of  the  class  mammalia,  which 
in  turn  is  only  a  branch  of  the  limb  vertebrata  or  chordata, 
which  also  bears  the  avaian,  reptilian,  amphibian  and  fish 
branches.  And  all  the  vertebrates  including  man  agree 
with  the  varied  groups  of  invertebrates  in  their  cellular 
constitution  and  in  the  similar  protoplasmic  basis  of  life. 
As  in  these  structural  respects,  so  in  physiological  activi- 
ties and  in  environmental  relations  the  human  species 
proves  more  surely  with  increased  knowledge  to  be  only 
one  of  the  terms  in  the  extensive  series  of  animals.  In- 
deed, the  scientific  monism  of  Haeckel  and  Clifford  ven- 
tures to  assert  that  man  and  all  other  living  creatures  are 
one  with  the  mind-stuff  of  the  inorganic  world — and  this, 
I  believe,  is  only  the  logical  extension  of  the  genetic  and 
mechanistic  hypotheses.  However  this  may  be,  science 
holds  that  human  structure  is  animal  structure,  and  that 
human  lives  are  biological  phenomena. 

Man  is  structurally  inferior  in  many  respects  to  some 
of  his  zoological  relatives — he  is  a  degenerate,  indeed,  in 
many  parts  of  the  alimentary,  muscular  and  skeletal  sys- 

27 


terns— yet  he  finds  in  the  higher  development  of  his  ner- 
vous system  an  advantage  that  offsets  the  weaknesses  of 
his  constitution  elsewhere.  He  holds  his  supreme  place 
by  virtue  only  of  superior  and  more  effective  control  of 
his  organization. 

Behind  their  seeming  structural  differences,  only  one  real 
distinction  can  be  found  to  separate  man  from  the  apes— 
the  higher  development  of  the  brain.  The  erect  posture,  the 
correlated  modifications  of  skeletal  and  muscular  struc- 
tures, and  apparently  the  powers  of  speech  and  reason, 
seem  to  be  dependent  upon  the  enlargement  of  this  organ, 
which,  so  to  speak,  has  pushed  the  face  around  under  the 
brain-case.  Therefore  he  who  would  be  6  avOpcuTros — 
he  who  looks  ahead— must  needs  stand  erect  in  order  to 
prevent  his  eyes  from  looking  straight  into  the  ground. 
But  the  most  careful  analysis  has  so  far  failed  to  detect 
any  essential  differences  in  either  structural  or  functional 
respects  between  the  human  brain  and  the  corresponding 
organs  of  the  higher  apes.  In  brief,  then,  differences  in 
degree  and  not  in  kind  or  category  seem  to  distinguish 
man  from  the  apes — as  far  as  science  goes. 

Moreover,  the  human  body  is  a  veritable  museum  of 
rare  and  interesting  relics  of  antiquity — the  useless  ves- 
tiges and  rudiments  of  structures  that  are  more  developed 
in  other  animals.  The  complete  coat  of  hair  of  the  embryo, 
the  disappearing  thirteenth  rib,  the  ape-like  and  transi- 
tory clasping  muscle  of  the  new  born  infant's  hand,  the 
curvature  of  the  lower  limb  and  the  hand-like  foot  of  the 
embryo,  these  and  scores  of  other  characters  are  mutely 
eloquent  witnesses  to  the  past  history  of  change  that  has 
brought  man  to  his  present  place  in  nature.  Embryology 
gives  a  vast  amount  of  additional  independent  testimony. 
For  like  all  embryo  mammals  and  birds  and  reptiles,  the 
human  embryo  possesses  gill-slits,  and  fish-like  heart  and 
brain.  Above  all  it  begins  life  as  a  single  cell.  Zo- 

28 


ology  asks: — What  can  these  things  mean,  if  they  do  not 
mean  evolution  and  a  common  ancestry  with  other  forms? 
The  objection  that  no  one  has  ever  seen  a  one-celled  organ- 
ism evolve  into  a  many-celled  one,  or  into  a  fish  or  an  ape, 
or  into  a  man,  the  zoologist  answers  by  placing  upon  the 
table  the  evidence  that  a  single-cell,  the  human  egg,  actu- 
ally does  compass  the  whole  history  in  becoming  the  almost 
inconceivably  complex  adult  organism.  The  process  can 
take  place  for  it  does  take  place.  Paleontology  also  pre- 
sents evidence  relating  to  the  history  of  our  species,  as  the 
third  support  of  the  tripod  upon  which  rests  the  doctrine 
of  human  evolution.  While  opinions  differ  with  respect 
to  the  remains  of  man  taken  from  the  many  caves  and 
mounds  of  Europe  and  America,  there  is  but  one  generally 
accepted  view  regarding  the  ape-man  Pithecanthropus  of 
the  Javan  rocks.  The  remains  of  this  animal  prove  among 
other  things  that  its  brain  was  intermediate  between  the 
average  ape  brain  and  the  average  human  brain,  that  the 
animal  wras  indeed  an  ape-man  and  nothing  else. 

Science  holds  furthermore  that  natural  factors  alone 
have  brought  about  human  evolution.  While  it  is  true  that 
the  explanation  is  no  more  complete  for  this  special  in- 
stance than  it  is  for  animals  in  general,  yet  the  human 
species  is  not  exempt  from  the  control  of  the  known  fac- 
tors, like  those  which  cause  variation  or  govern  inheritance. 
Indeed  some  of  the  significant  facts  of  heredity  have  been 
first  made  out  in  the  human  species.  Can  we  doubt  the 
reality  of  selection  and  the  struggle  for  existence  when 
scoreis  perish  annually  in  the  conflict  with  extreme  degrees 
of  temperature  and  other  environmental  forces,  when  as  a 
result  of  the  unceasing  combat  with  bacterial  enemies , 
alone  the  casualties  on  the  human  side  number  in  our  coun- 
try more  than  a  hundred  thousand  annually? 

To  the  zoologist  it  seems  strange  that  there  is  so  much 
opposition  to  the  doctrine  of  human  evolution.     In  truth 

29 


he  finds  this  to  be  proportional  to  misunderstanding  of 
the  facts,  for  when  the  evidence  is  produced — Pelion  piled 
on  Ossa — any  lingering  doubts  the  observer  might  have 
are  crushed  by  an  irresistible  weight  of  testimony.  After 
all,  our  kind  is  but  one  of  the  many  hundreds  of  thousands 
of  living  species;  and  viewing  the  matter  from  the  calm, 
impersonal  standpoint  of  scientific  study,  the  fact  that  he 
is  himself  a  human  being  does  not  distort  the  investigator's 
vision,  for  his  perspective  is  corrected  and  rectified  by  the 
instruments  of  scientific  method.  He  finds  no  difficulty 
in  accepting  human  evolution  as  a  scientific  fact — that  is, 
true  as  far  as  science  goes. 


IN  extending  its  broad  comparative  studies  into  the  field 
of  complex  and  intricate  human  nature,  zoology  touches 
numerous  other  sciences  that  might  seem  at  first  sight  to  be 
entirely  independent,  or  at  the  most  only  casually  con- 
nected with  it.  I  shall  venture  to  point  out  where  analysis 
within  the  field  of  zoology  has  produced  results  which  have 
a  high  and  immediate  value  for  students  of  anthropology, 
psychology,  sociology  and  ethics. 

When  they  deal  with  the  evolution  of  the  human  species 
from  pre-human  animals,  the  anthropologist  and  the 
zoologist  are  brought  by  their  similar  interest  upon  com- 
mon ground;  and  when  they  pass  on  to  explore  the  field 
of  human  diversity  where  lie  the  complex  problems  of 
racial  evolution,  they  are  still  fellow-workers,  for  in  the 
case  of  physical  anthropology  of  human  races  at  least  the 
methods  are  the  same  which  are  employed  in  zoology  gen- 
erally. Of  course  it  would  be  absurd  for  anyone  to  contend 
that  all  the  problems  of  anthropology  are  strictly  zoologi- 
cal questions;  to  qualify  here  an  investigator  must  be 
familiar  with  linguistics,  racial  customs  and  beliefs,  and 
many  subjects  that  are  as  such  apparently  outside  the 

30 


limits  of  zoology.  But  unless  a  sharp  line  is  to  be  drawn 
between  the  slow  origin  by  evolution  of  the  human  species 
and  the  later  history  of  this  species,  the  comparative  and 
genetic  methods  of  analysis  which  render  the  earlier  pro- 
cess intelligible  can  scarcely  fail  to  be  of  service  in  dealing 
with  the  latter.  The  great  danger,  which  the  zoologist 
himself  clearly  sees,  arises  from  a  tendency  to  ignore  the 
detail  in  formulating  the  general,  to  oversimplify  the 
problems  of  the  more  recent  history.  For  human  con- 
scious elements  are  so  complex  and  plastic  that  the  prob- 
lems of  racial  evolution  are  rendered  far  more  intricate 
than  the  broad  zoological  analysis  of  the  origin  of  man  as  a 
species. 

Psychology,  in  the  second  place,  is  a  subject  that  is  re- 
lated to  zoology  by  the  closest  of  ties,  the  bond  of  union 
being  again  the  common  human  element.  To  be  sure  the 
zoologist  finds  enough  in  his  own  field  to  occupy  him  fully, 
but  the  comparative  study  of  nervous  systems,  and  of  the 
reflex,  instinctive,  intelligent,  and  reasoned  responses  of 
animals  brings  him  inevitably  to  consider  the  relation  of 
human  mentality  and  consciousness  to  the  other  terms  of 
the  animal  series.  Dealing  strictly  as  a  zoologist  with 
animals  and  their  lives,  the  investigator  learns  that  the 
machine-like  regularity  of  reflex  and  instinctive  activities 
is  correlated,  broadly  speaking,  with  simple  nervous  or- 
ganization ;  that  the  plasticity  of  intelligent  response  is  not 
gained  until  the  physical  basis  becomes  far  more  compli- 
cated; and  finally  that  reason  and  consciousness  are  in 
some  way  bound  up  with  the  higher  development  of  the 
nerve-centers  or  ganglia  that  make  up  the  brain.  So  the 
zoologist  is  inclined  to  believe  that  the  comparative  series 
of  mental  grades  which  culminates  in  the  consciousness, 
or  rather  the  self -consciousness  of  the  adult  human  organ- 
ism, and  the  series  of  developmental  stages  through  which 
the  human  mental  structure  passes  during  infancy  and 

31 


childhood,  indicate  an  evolution  in  time  of  the  psychic  be- 
ing of  man.  Whatever  may  be  the  outcome  of  further 
study,  Romanes,  Lloyd  Morgan,  Forel  and  Thorndike, 
among  those  of  modern  times,  have  demonstrated  that  the 
genetic  methods  of  zoology  are  useful  instruments  for  the 
psychologist,  who,  I  believe,  is  becoming  more  and  more 
a  student  of  zoological  materials  as  he  realizes  the  ad- 
vantage of  studying  the  simpler  psychic  phenomena  of 
animals  lower  than  man. 

In  venturing  to  speak  of  the  relation  of  zoology  to 
sociology  and  ethics,  I  am  well  aware  that  I  shall  be 
charged  with  straying  beyond  the  confines  of  my  subject. 
But  if  the  student  of  lower  forms  should  find  well-defined 
principles  of  biological  association  and  principles  of  ani- 
mal conduct,  it  is  not  only  his  privilege,  it  is  in  a  sense  his 
duty  as  well  to  bring  these  to  the  consideration  of  the 
students  of  human  social  and  ethical  relations.  Unless  in 
these  matters  there  has  been  a  break  in  the  continuity  of 
evolution,  the  simpler  relations  to  be  observed  in  lower 
animals  must  surely  possess  a  profound  interest — and  per- 
haps more. 

In  a  true  sense,  any  of  the  many-celled  animals  is  a 
community,  whose  constituent  members  are  the  differ- 
entiated tissue-cells,  which  have  undertaken  the  various 
tasks  of  digestion,  contraction,  sensation,  and  the  rest. 
By  far  the  majority  of  animals  are  cell-communities  of 
this  nature.  Considering  these  as  individuals,  though  of 
a  secondary  order,  we  find  some  communities  made  up  of 
several  animals  which  have  banded  together  for  mutual 
support  and  defense,  giving  us  as  in  the  wolf -pack  a  coun- 
terpart of  the  lowest  associations  of  savage  men.  But 
among  insects  especially  we  find  colonies  of  numerous 
multicellular  individuals  which  may  be  so  rigidly  special- 
ized for  the  performance  of  certain  tasks  that  we  cannot 
avoid  the  use  of  terms  applied  to  civilized  human  groups 

32 


in  describing  their  differentiation  and  division  of  labor. 
Some  colonies  of  bees  comprise  queens  and  drones  and 
only  one  kind  of  sterile  workers,  though  when  newly  hatched 
these  last  serve  as  guards  and  nurses,  taking  the  field  as 
foragers  for  pollen  and  honey  only  later  in  life.  In  various 
ant-colonies  we  will  find  workers  who  serve  as  herdsmen, 
devoting  their  time  to  the  care  of  the  ant-cattle  or  aphids ; 
again  there  are  masons,  and  gardeners,  and  carpenters,  and 
soldiers  of  various  ranks,  while  in  the  honey-ant  some  indi- 
viduals may  serve  as  living  receptacles  for  the  tribal  stores 
of  food.  Each  kind  undertakes  one  of  the  tasks  that  are 
vital  for  the  life  of  the  community  as  a  whole.  Instinctive 
and  unreasoned  their  activities  may  be,  and  undoubtedly 
are,  but  the  economic  and  social  relations  of  the  component 
members  of  the  colony  are  strikingly  analogous  to  certain 
fundamental  phenomena  of  human  societies.  But  still 
more  wonderful  are  the  cases  that  may  be  found  among 
hornets  and  wasps.  A  fertile  female  overwinters  and 
places  her  first-laid  eggs  in  the  chambers  of  a  simple  nest 
that  she  constructs  herself.  When  the  young  of  the  first 
brood  hatch,  she  provides  them  with  food,  enlarges  the  nest, 
and  continues  the  task  of  egg-laying,  while  her  first  off- 
spring relieve  her  of  her  former  duties  as  they  become  able. 
They  enlarge  the  nest,  they  care  for  their  younger  kin  as 
they  hatch,  they  forage  abroad  for  the  food-supplies  for 
the  colony.  And  so  the  community  that  begins  life  in  the 
early  spring  with  a  solitary  animal  advances  during  the 
passing  weeks  to  a  degree  of  complexity  that  is  truly 
astounding.  As  an  epitome  of  insect  social  evolution  it 
gives  in  a  few  weeks  a  review  of  the  process  that  in  other 
forms  of  social  insects  with  stable  colonies,  or  in  the  anal- 
ogous human  history,  has  demanded  centuries  of  time. 

As  we  review  these  different  kinds  of  individuals — the 
one-celled  animal,  the  many-celled  creature  and  the  com- 
munity,— we  see  that  each  one  must  obey  certain  rules  of 


nature.  It  must  preserve  itself,  it  must  perpetuate  its 
kind,  and,  if  it  be  a  member  of  a  higher  community,  it 
must  act  in  the  interests  of  others  and  of  the  whole  group. 
Do  we  not  find,  then,  biological  definitions  of  right,  and 
evil,  and  duty  to  others  as  well  as  to  self?  Do  we  not  see 
why  altruism  has  grown  out  of  egoism  as  communities 
have  evolved  at  the  behest  of  nature? 

But  still,  facts  like  these  are  purely  zoological  facts.  To 
be  well  within  his  rights,  the  zoologist  should  perhaps  only 
suggest  their  usefulness  for  the  analysis  of  human  social 
relations  and  obligations.  It  is  for  the  sociologist  and  the 
student  of  comparative  ethics  to  employ  and  apply  them 
according  to  the  principles  of  the  genetic  method,  should 
they  see  fit  to  do  so. 


IN  closing,  may  I  say  a  few  words  regarding  the  attitude 
of  the  zoologist  toward  his  problems  and  his  results.  He 
may  maintain  this  attitude  because  of  a  certain  tempera- 
ment which  leads  him  and  his  fellows  to  enter  the  field  of 
science  as  investigators.  While  this  may  be  true,  it  is  also 
true,  I  believe,  that  the  subjects  of  their  study,  the  prin- 
ciples they  may  discern  in  nature's  order,  and  their  meth- 
ods of  analysis  have  a  profound  reflex  effect  upon  not  only 
the  contents  of  their  minds  but  upon  their  mental  ma- 
chinery as  well.  The  zoologist,  like  his  fellow  men  of 
science,  learns  early  that  he  must  adopt  an  impersonal  atti- 
tude, for  emotion  and  purely  human  interest  are  disturb- 
ing elements  that  prevent  him  from  attaining  the  purpose 
of  the  investigator — which  is,  to  ascertain  and  verify  facts, 
to  classify  them  logically,  so  as  to  derive  from  them  the 
summaries  which  like  so  much  "conceptual  short-hand"  are 
available  for  others  as  well  as  himself.  Science  is  "organ- 
ized knowledge,"  as  Pearson  defines  it;  "organized common 
sense"  in  Huxley's  phrase ;  and  like  other  men  of  science  the 

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zoologist  learns  to  view  his  great  common-sensible  princi- 
ples like  the  doctrine  of  descent,  not  as  absolute  eternal 
verities,  but  only  as  summaries  up  to  date,  as  working  pro- 
grams, to  employ  Professor  Wilson's  concise  phrase.  This 
may  be  pragmatism ;  it  is  certainly  science. 

But  surely  this  does  not  mean  that  principles  like  the  one 
mentioned  are  so  many  gratuitous  assumptions.  Like  the 
principle  of  gravitation  and  the  law  of  the  conservation  of 
energy,  zoological  laws  have  the  strength  and  approximate 
finality  of  all  the  wide  range  of  facts  that  they  summarize. 
And  these  are  many — a  vast  store  of  detail  and  generaliza- 
tion accumulated  during  decades  and  centuries  by  those 
who  have  sought  upon  the  mountains  or  in  the  abysses  of 
the  seas  for  new  knowledge,  by  countless  students  who 
have  spent  their  lives  in  the  field  and  in  the  laboratory  in 
the  endeavor  to  pierce  still  further  with  trained  insight 
into  the  mysteries  of  nature.  And  these  are  their  results. 

No  one  realizes  more  than  the  zoologist  that  his  know- 
ledge is  incomplete.  No  one  can  see  more  clearly  than  he 
that  his  intellect  evolves,  like  the  great  sweeping  tide 
of  things  and  events — the  nature  he  studies  and  of  which 
he  is  but  a  conscious  atom.  The  investigator  soon  learns  to 
withhold  final  judgment,  agreeing  with  Clifford  that  the 
primary  conditions  for  intellectual  development  are  the 
plasticity  and  openness  of  mind  that  dogmatism  and  final- 
ity destroy.  The  end  of  zoology  cannot  be  until  the  end  of 
all  knowledge. 

Conscious  then  of  the  impossibility  of  reaching  abso- 
lutely final  knowledge,  why  does  the  investigator  continue 
to  search  the  world  of  nature  as  he  does  ?  Because  of  that 
ingrained  and  insatiable  human  curiosity  to  learn,  because 
of  the  human  discontent  with  the  attained.  Antaeus-like, 
every  fresh  contact  with  the  world  of  law  and  order  infuses 
new  energy  into  his  veins  for  further  endeavor.  "Und  es 
treibt  und  reisst  ihn  fort,  rastlos  fort  ..."  not,  it  is  true, 

35 


in  the  wandering  blindness  of  Schiller's  huntsman,  for  his 
human  vision  is  aided  by  the  instrument  of  scientific 
method  with  which  he  can  almost  perceive  the  infinitely 
great  and  the  infinitely  small. 

Glorying  in  the  great  achievements  of  his  science,  revel- 
ing like  the  mathematician  in  the  ordered  assemblage  of 
related  and  organized  knowledge,  the  student  of  zoology 
joins  his  fellows  yet  again  for  a  renewed  attack  upon  the 
distant  ramparts  of  the  unknown,  deriving  courage  and 
inspiration  from  the  motto :  Ignoramus,  in  hoc  signo  labo- 
remus. 


36 


